Machining and Joining Tungsten Alloys
Machining Tungsten Alloys
Sometimes, you can have it all. Our high-density tungsten alloys are extremely strong and durable (typical hardness ranges from 24-32 RC), yet easy to work with. (They machine much like gray cast iron.) Tungsten alloy’s low-thermal expansion rate and resistance to breakage and chipping allow you to achieve very close tolerances and hold fine finishes. Coolants are optional, reducing your processing costs and, in most cases, your carbide tools will machine our high-density alloys well.
Turning
Positive rake tooling is suggested. Seco triangle inserts TPG432 or TPG431 grade 883.
Boring
No rake or positive rake tooling is suggested. Seco CPMT grade 883.
Roughing
Cutting depth of .030” to .125” and .008” to .015” feed, at 200 to 300 SFM.
Finishing
.010” to .015” cutting depth and .004” to .010” feed at 250 to 400 SFM.
Tapping
Use high-speed steel, two flute plug spiral point taps. A light tapping fluid is recommended or vegetable oil mist. OSG Sossner premium Exotap is suggested.
Drilling
Carbide tooling is suggested. Increased clearance angles and automatic feeds are often used to avoid binding and seizing. Carbide drills will give a better tool life.
Grinding
Use aluminum oxide or silicon carbide wheels of medium hardness.
Milling
Premium uncoated end mills with a regular spiral made from micrograin carbide, such as SGS. Insert cutters; use square multi-edge or single edge cutters, such as Kennametal grade KC730. Also can use positive rake octagon cutters, such as Seco grade 883.
Roughing
Feeds of .007” to .015” per tooth at speeds of 200 to 400 SFM.
Finishing
Feeds of .003” to .010” per tooth at speeds of 300 to 700 SFM.
Sawing or Cutting
When sawing, use a bi-metal blade; blade pitch should be relative to the thickness of the material. Coarse blades can be run at low speeds, and finer blades run at higher speeds. Coolant can be used. Material can also be cut using high-speed abrasive cutoff wheels.
Stress Relieving
Stress relieving can be accomplished on machined parts. We suggest heating at 600°F in air for two hours and cool in air or in a protective atmosphere at 900°F for 30 minutes.
Stiffness, Machinability
| Material | Stiffness | Machinability |
|---|---|---|
| Tungsten Carbide | 75-90 | Difficult |
| Osmium, Iridium | 80 | Bad |
| Tungsten(Pure) | 59 | Poor |
| TZM | 57 | Poor |
| Molybdenum | 53 | Fair |
| HD 17.7, HD 18.5 | 53 | Fair-Good |
| HD 18, HD 18D | 50 | Fair-Good |
| HD 17.5 | 45 | Fair-Good |
| HD 17, HD 17D, HD 17BB | 40 | Good |
| Cobalt, Nickel | 36 | Fair |
| Steel | 28-30 | Good(Must be H.T.) |
Mechanical Joining
Mechanical joining is the best option for joining high-density alloy material. Standard fasteners such as bolts and pins are often used, as is threading a tungsten alloy to mate to itself.
Shrink Fitting
Shrink fitting is another good method to join tungsten alloy to steel. Depending on the size of the part, .005"/.007" interference per side is recommended. The high-density alloy is chilled in dry ice or nitrogen while the steel is heated. The resulting joint is usually reinforced with a pin or fixture and allowed to cool slowly.
Contact a Mi-Tech Metals professional for more information on which method would be best for your application.
